CN112228079A

CN112228079A - Construction method for newly-built tunnel to span existing line at small angle

Info

Publication number: CN112228079A
Application number: CN202011091336.5A
Authority: CN
Inventors: 刘顿; 熊勇军; 陈兴强; 张转转; 郭新平; 须言; 李传华; 陈雷; 唐伟伟; 穆文博; 刘君; 杨润东
Original assignee: China Railway No 10 Engineering Group Co Ltd; Urban Rail Transit Engineering Co Ltd of China Railway No 10 Engineering Group Co Ltd
Current assignee: China Railway No 10 Engineering Group Co Ltd; Urban Rail Transit Engineering Co Ltd of China Railway No 10 Engineering Group Co Ltd
Priority date: 2020-10-13
Filing date: 2020-10-13
Publication date: 2021-01-15
Anticipated expiration: 2040-10-13
Also published as: CN112228079B

Abstract

The invention discloses a construction method for spanning an existing line at a small angle of a newly built tunnel, which comprises the following steps: determining a tunnel excavation boundary line; digging a middle pilot hole; excavating an upper step channel; excavating a right channel of the middle step; excavating a middle step left channel, wherein L4 is smaller than L3, and then primarily spraying concrete on the rock wall of the middle step left channel; excavating a left channel of the lower step; and (5) excavating a right channel of the lower step forwards, and applying corresponding primary support. The method adopts a three-step method and a middle pilot tunnel in advance step-by-step blasting excavation, and is suitable for blasting excavation of existing lines spanning small angles of various newly-built tunnels. The method has the advantages of applicability, capability of rapidly vacating a working face and immediately performing primary support through the step-by-step blasting excavation of the middle pilot tunnel, more reasonable process connection and effective acceleration of construction progress.

Description

Construction method for newly-built tunnel to span existing line at small angle

Technical Field

The invention relates to the field of tunnel construction, in particular to a construction method for spanning an existing line at a small angle of a newly-built tunnel.

Background

With the strong promotion of infrastructure, the tunnel construction business of China is rapidly developed. According to statistics, the business mileage of China railway reaches 13.1 km by the beginning of 2020. Wherein, the length of the 15117 seats of the railway tunnel operated by the person is 16331 km. Due to the fact that railway tunnel construction lines are increased continuously and traffic line networks are dense continuously, when a tunnel is built newly, engineering construction is limited by actual geological and topographic conditions, land acquisition range and environmental protection requirements, existing railway lines need to be crossed upwards or downwards frequently, and the difficulty in building new lines is increased greatly.

Blasting excavation is still the main construction means of newly-built tunnels at present. When a newly-built tunnel is close to an existing railway tunnel, the buried depth of surrounding rocks of an upper span section or a lower span section is generally shallow, the quality of the surrounding rocks is relatively common, adverse effects are easily caused on an existing line supporting structure during blasting excavation, and particularly when the blasting vibration peak value exceeds the limit, the damage of an existing line lining structure is easily caused, so that the existing line structure is cracked and unstable, the speed reduction, the speed limit and even the shutdown of a line are caused, and the social adverse effects are caused. Therefore, how to ensure the orderly excavation operation of the newly-built line and ensure the safe and undamaged existing line structure and the orderly operation is a major difficulty faced by engineering technicians, designers and scientific researchers at present.

Disclosure of Invention

The invention aims to solve the technical problem of providing a construction method for newly building a tunnel to span an existing line at a small angle, which can realize minimum disturbance on the existing line at the small angle.

In order to solve the technical problems, the invention adopts the following technical scheme: the construction method for spanning the existing line at a small angle of a newly-built tunnel comprises the following steps:

(1) determining a tunnel excavation boundary line, determining an upper step excavation boundary line and a lower step excavation boundary line in the tunnel excavation boundary line, and determining a middle pilot tunnel excavation boundary line in the tunnel excavation boundary line and above the upper step excavation boundary line;

(2) excavating a middle pilot tunnel with the length of L1 forwards along an area surrounded by the middle pilot tunnel excavation boundary line and the part, located in the middle pilot tunnel excavation boundary line, of the upper step excavation boundary line, and then primarily spraying concrete on the rock wall of the middle pilot tunnel;

(3) an upper step channel with the length of L2 is excavated forwards along an area defined by a middle pilot tunnel excavation boundary line, a part of an upper step excavation boundary line, which is positioned outside the middle pilot tunnel excavation boundary line, and a part of a tunnel excavation boundary line, which is positioned above the upper step excavation boundary line, and then concrete is primarily sprayed on the rock wall of the upper step channel;

(4) constructing primary supports of the middle pilot tunnel and the upper step channel;

(5) excavating a middle-step left channel with the length of L3 forwards along the left half part of a region surrounded by the upper-step excavation boundary line, the lower-step excavation boundary line and the part, located between the upper-step excavation boundary line and the lower-step excavation boundary line, of the tunnel excavation boundary line, wherein L3 is smaller than L2, and then primarily spraying concrete on the rock wall of the middle-step left channel;

(6) excavating a middle-step right channel with the length of L4 forwards along the right half part of a region surrounded by the parts, located between the upper-step excavation boundary line and the lower-step excavation boundary line, of the upper-step excavation boundary line, the lower-step excavation boundary line and the tunnel excavation boundary line, wherein L4 is smaller than L3, and then primarily spraying concrete on the rock wall of the middle-step right channel;

(7) constructing primary supports of the middle step left channel and the middle step right channel;

(8) a lower step left channel with the length of L5 is excavated forwards along the left half part of a region surrounded by the lower step excavation boundary line and the part, located below the lower step excavation boundary line, of the tunnel excavation boundary line, L5 is smaller than L4, and then concrete is primarily sprayed on the rock wall of the lower step left channel;

(9) excavating a lower step right channel with the length of L6 forwards along the right half part of a region surrounded by the lower step excavation boundary line and the part, located below the lower step excavation boundary line, of the tunnel excavation boundary line, wherein L6 is smaller than L5, and then primarily spraying concrete on the rock wall of the lower step right channel;

(10) and constructing primary supports of the lower step left channel and the lower step right channel.

Further, the method also comprises the step (11): and (3) pouring inverted arches at the bottoms of the front ends of the left channel and the right channel of the lower step, filling the inverted arches, and finally pouring secondary lining.

Furthermore, blasting excavation modes are adopted for the middle pilot tunnel, the upper step channel, the middle step left channel, the middle step right channel, the lower step left channel and the lower step right channel.

Further, the concrete construction method of the primary support comprises the following steps: the concrete is sprayed firstly, then the anchor rod group is installed, then the reinforcing mesh is laid, finally the steel grating arch is installed, and the anchor rod group is connected with the steel grating arch.

Further, the anchor rod group comprises a plurality of hollow grouting anchor rods and a plurality of mortar anchor rods, the hollow grouting anchor rods are arranged in a quincunx shape along the circumferential direction and the longitudinal direction of the steel grating arch center, and the mortar anchor rods are arranged at the arch crown and the arch waists on the two sides.

Furthermore, the hollow grouting anchor rod is provided with external threads, the hollow grouting anchor rod is sequentially divided into an anchoring section, a concrete lining section and a template reinforcing section from top to bottom, the anchoring section of the hollow grouting anchor rod is embedded in the tunnel rock wall through an anchoring agent, the hollow grouting anchor rod is sleeved with a sealing ring, a water stop steel ring and a first nut, the sealing ring and the water stop steel ring are clamped between the tunnel rock wall and the first nut, the sealing ring is tightly attached to the tunnel rock wall, and the concrete lining section of the hollow grouting anchor rod is connected with the steel grating arch frame.

Furthermore, the upper ends of the hollow grouting anchor rod and the mortar anchor rod are respectively provided with an anchor head, the anchor heads comprise V-shaped elastic pieces fixed on the hollow grouting anchor rod or the mortar anchor rod and springs sleeved on the hollow grouting anchor rod or the mortar anchor rod, strip-shaped holes are respectively formed in two sides of each elastic piece, and the wall of the upper side hole of each strip-shaped hole is connected with a clamping jaw which is bent outwards.

Furthermore, the steel grating arch comprises an outer ring main rib and an inner ring main rib which are both arc-shaped, and a plurality of supporting and reinforcing mechanisms welded between the outer ring main rib and the inner ring main rib; support reinforcing mechanism and include that two fronts are the 8 fonts, the side is the basic reinforcing bar of V-arrangement, two mutual symmetries of basic reinforcing bar and middle part welding link to each other for the side that supports reinforcing mechanism is the X-arrangement, a plurality of installation direction staggered designs that support reinforcing mechanism, in arbitrary two adjacent support reinforcing mechanism, one of them side that supports reinforcing mechanism is towards outer loop owner muscle, another installation direction that supports reinforcing mechanism and this one of them contained angle that supports between the installation direction of reinforcing mechanism are 90 degrees.

Furthermore, support reinforcing mechanism still includes two ring reinforcing bars, and two ring reinforcing bars support respectively between the both sides of two basic steel bars and with two basic steel bar welded connection.

The invention has the beneficial effects that:

on the basis of analyzing the propagation and attenuation rules of blasting vibration of weakly weathered granite stratums, in order to prevent the adverse effect of blasting of a newly built line on the operation of an existing line, the minimum disturbance of the existing line over a small angle is realized by adopting a three-step method and a middle pilot hole advance mode, and the method has the following advantages:

1. the applicability is strong. The method adopts a three-step method and a middle pilot tunnel in advance step-by-step blasting excavation, and is suitable for blasting excavation of existing lines spanning small angles of various newly-built tunnels.

2. The construction speed is high. The middle pilot tunnel is firstly blasted and excavated step by step to quickly vacate a working face and can be immediately applied to primary support, the working procedures are more reasonable to join, and the construction progress is effectively accelerated.

3. The safety is high. According to the construction method, the preliminary bracing progress can be accelerated on the premise of not increasing the construction cost by adopting a 'pilot tunnel advance' and 'graded construction' mode, and the occurrence and development of large deformation of the super-large-span tunnel can be effectively controlled by utilizing the self stability of surrounding rocks, so that the construction method is more favorable for construction safety.

4. The disturbance is small. The construction method can reduce the disturbance to the existing line to the maximum extent through the digital electronic detonator and the effective blasting and damping construction method.

Drawings

FIG. 1 is a schematic illustration of excavation boundaries in accordance with an embodiment of the present invention.

Figure 2 is a schematic illustration of an excavation process according to one embodiment of the present invention.

Fig. 3 is a schematic diagram of the excavation areas of each step in one embodiment of the present invention.

FIG. 4 is a schematic longitudinal sectional view of the construction according to an embodiment of the present invention.

FIG. 5 is a cross-sectional view of a lining in an embodiment of the present invention.

Fig. 6 is a schematic view of the installation of a mortar anchor in an embodiment of the invention.

Fig. 7 is a structure diagram of the blasting excavation construction space charge in one embodiment of the invention.

Fig. 8 is a schematic diagram of the distribution of blastholes in blasting excavation according to an embodiment of the present invention.

Fig. 9 is a schematic view of the installation structure of the hollow grouting bolt according to an embodiment of the present invention.

Fig. 10 is a top view of the pallet and associated structures of fig. 9.

Figure 11 is a schematic view of the structure of an anchor head in an embodiment of the invention.

Figure 12 is a left side view of the anchor head of figure 11.

Fig. 13 is a schematic structural view of a steel grating arch according to an embodiment of the present invention.

Fig. 14 is a schematic structural view of the support reinforcement mechanism of fig. 13.

Fig. 15 is a top view of fig. 14.

Fig. 16 is a cross-sectional view of fig. 14.

Fig. 17 is a schematic view of the installation of a mortar anchor in accordance with an embodiment of the present invention.

Fig. 18 is an end view of a steel grating arch in an embodiment of the present invention.

Fig. 19 is a schematic illustration of the splicing of a steel grating arch in an embodiment of the invention.

Fig. 20 is a schematic view of the steel grating arch in the expanded and longitudinally connected reinforcing bars according to an embodiment of the present invention.

The components in the drawings are labeled as follows:

an X1 tunnel excavation boundary line, an X2 upper step excavation boundary line, an X3 lower step excavation boundary line and an X4 middle pilot tunnel excavation boundary line;

a pilot tunnel in O1, an O2 upper step channel, an O3 middle step left channel, an O4 middle step right channel, an O5 lower step left channel and an O6 lower step right channel;

11 hollow grouting anchor rods, 111 anchoring sections, 112 concrete lining sections, 113 formwork reinforcing sections, 114 limiting flanges, 12 sealing rings, 13 water stop steel rings, 14 first nuts, 15 anchor heads, 151 elastic sheets, 152 springs, 153 strip-shaped holes, 154 claws, 16 supporting plates, 161 strip-shaped notches, 162 insertion holes, 17 insertion steel bars, 171V-shaped sections, 172 insertion sections, 18 second nuts, 191 formworks, 192 square timbers and 193 steel pipes;

21 outer ring main reinforcements, 22 inner ring main reinforcements, 201 reinforcement rods, 202 first reinforcements, 203 second reinforcements, 23 support reinforcing mechanisms, 231 foundation reinforcements, 232 ring reinforcements, 24 hoops, 241 first mounting rings, 242 second mounting rings, 25 connecting angle steels, 26 bolt holes and 27 mortar anchor rods;

31 explosive, 32 stemming, 33 bamboo chips, 34 detonating cords and 35 non-electric millisecond detonators.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The embodiments and features of the embodiments in the present application may be combined with each other without conflict. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that, if directional indications (such as up, down, left, right, front, and back … …) are involved in the embodiment of the present invention, the directional indications are only used to explain the relative positional relationship between the components, the movement situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indications are changed accordingly.

In addition, if there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and/or" appearing throughout includes three juxtapositions, exemplified by "A and/or B" including either A or B or both A and B. In addition, "a plurality" means two or more. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

See fig. 1-4. Hatching in fig. 3 does not indicate a cross section of the object, but is used to indicate a corresponding excavated area or poured area, and fig. 4 illustrates that the excavation proceeds from left to right.

The invention discloses a construction method for newly building a tunnel to span an existing line at a small angle, which comprises the following steps:

(1) determining a tunnel excavation boundary line X1, determining an upper step excavation boundary line X2 and a lower step excavation boundary line X3 in the tunnel excavation boundary line X1, and determining an inverted U-shaped middle pilot tunnel excavation boundary line X4 above the upper step excavation boundary line X2 in the tunnel excavation boundary line X1;

(2) a middle pilot tunnel O1 with the length of L1 is excavated forwards along an area defined by the middle pilot tunnel excavation boundary line X4 and the part, located in the middle pilot tunnel excavation boundary line X4, of the upper step excavation boundary line X2, and then concrete is sprayed on the rock wall of the middle pilot tunnel O1 in a primary mode;

(3) an upper step passage O2 with the length of L2 is excavated forwards along an area defined by a middle pilot tunnel excavation boundary line X4, a part of an upper step excavation boundary line X2, which is positioned outside a middle pilot tunnel excavation boundary line X4, and a part of a tunnel excavation boundary line X1, which is positioned above an upper step excavation boundary line X2, and L2 is smaller than L1, and then concrete is primarily sprayed on the rock wall of the upper step passage O2;

(4) constructing primary supports of a middle pilot tunnel O1 and an upper step channel O2;

(5) a middle step left channel O3 with the length of L3 is excavated forwards along the left half part of a region surrounded by the parts, located between the upper step excavation boundary line X2 and the lower step excavation boundary line X3, of the upper step excavation boundary line X2, the lower step excavation boundary line X3 and the tunnel excavation boundary line X1, L3 is smaller than L2, and then concrete is sprayed on the rock wall of the middle step left channel O3 in a primary mode;

(6) excavating a middle step right channel O4 with the length of L4 forwards along the right half part of a region surrounded by the parts, located between the upper step excavation boundary line X2 and the lower step excavation boundary line X3, of the upper step excavation boundary line X2, the lower step excavation boundary line X3 and the tunnel excavation boundary line X1, wherein the L4 is smaller than the L3, and then primarily spraying concrete on the rock wall of the middle step right channel O4;

(7) constructing primary support of a middle-step left channel O3 and a middle-step right channel O4;

(8) excavating a lower step left channel O5 with the length of L5 forwards along the left half part of a region surrounded by the lower step excavation boundary line X3 and the part, located below the lower step excavation boundary line X3, of the tunnel excavation boundary line X1, wherein L5 is smaller than L4, and then primarily spraying concrete on the rock wall of the lower step left channel O5;

(9) excavating a lower step right channel O6 with the length of L6 forwards along the right half part of a region surrounded by the lower step excavation boundary line X3 and the part, located below the lower step excavation boundary line X3, of the tunnel excavation boundary line X1, wherein L6 is smaller than L5, and then primarily spraying concrete on the rock wall of the lower step right channel O6;

(10) and performing primary support of a lower-step left channel O5 and a lower-step right channel O6.

In one embodiment, the method further comprises the step (11) of pouring an inverted arch at the bottom of the front end of the lower step left channel and the front end of the lower step right channel, then filling the inverted arch, and finally pouring a secondary lining.

In one embodiment, the specific construction method of the primary support is as follows: the concrete is sprayed firstly, then the anchor rod group is installed, then the reinforcing mesh is laid, finally the steel grating arch is installed, and the anchor rod group is connected with the steel grating arch. Design like this, preliminary bracing's structure is more stable, and steel grating bow member non-deformable is difficult for collapsing.

In one embodiment, referring to fig. 5 and 6, the anchor assembly includes a plurality of hollow grouting anchors 11 and a plurality of mortar anchors 27, the plurality of hollow grouting anchors 11 are arranged in a quincunx shape along circumferential and longitudinal directions of the steel grating arch, and the plurality of mortar anchors 27 are arranged at the arch crown and both side arch waists. The steel grating arch centering is poor in self-stability, potential safety hazards exist during construction, reinforcement measures must be taken, the problem can be effectively solved through the hollow grouting anchor rod and the mortar anchor rod, and the stability of the steel grating arch centering is guaranteed.

In the concrete implementation, the steel grating arch frame can be provided

L is 5m, and the thickness of the leg steel pipe 28 is 3.5 mm. Further increasing its stability.

In an embodiment, referring to fig. 9 and 10, an external thread is formed on the hollow grouting anchor rod 11, the hollow grouting anchor rod 11 is sequentially divided into an anchoring section 111, a concrete lining section 112 and a formwork reinforcing section 113 from top to bottom, the anchoring section 111 of the hollow grouting anchor rod 11 is embedded in a tunnel rock wall through an anchoring agent, a sealing ring 12, a water stop steel ring 13 and a first nut 14 are sleeved on the hollow grouting anchor rod 11, the sealing ring 12 and the water stop steel ring 13 are clamped between the tunnel rock wall and the first nut 14, the sealing ring 12 is tightly attached to the tunnel rock wall, and the concrete lining section 112 of the hollow grouting anchor rod 11 is connected with a steel grating arch frame. During construction, holes are drilled in the tunnel rock wall in a mechanical drilling mode, then the anchoring section of the hollow grouting anchor rod is inserted, anchoring agents are injected, the anchoring section is buried in the tunnel rock wall, reliable anchoring force is generated between the anchoring section and the tunnel rock wall, then the sealing ring, the water stop steel ring and the first nut are sleeved in the anchoring section, and the first nut is screwed down, so that water seepage at the drilling position can be effectively prevented through the rubber pad and the water stop steel ring, then the steel grating arch frame is connected with the concrete lining section, reliable pulling force is provided for the steel grating arch frame, the self-stability capacity of the steel grating arch frame is improved, the deformation of reinforcing steel bars is effectively controlled, and the construction difficulty is reduced.

In specific implementation, the length of the anchoring section 111 of the hollow grouting anchor rod 11 is not less than 1 meter, the sealing ring 12 is made of rubber, and the water stop steel ring 13 is made of a steel plate.

When concrete is poured, referring to fig. 9, the form 191 is installed again and reinforced with the square lumber 192 and the steel pipe 193 (the form reinforcing section 113 of the hollow grouting bolt 11, which can be used to install the reinforcing installation form 191, the square lumber 192, and the steel pipe 193), and then concrete is poured within the range of the concrete lining section 112. Preferably, the rear end of the formwork reinforcing section 113 of the hollow grouting bolt 11 is provided with a ring of radially outwardly extending stop flanges 114. The limiting flange is used for limiting the steel pipe, and the stability of the template is improved.

In a specific implementation, the concrete lining section 112 of the hollow grouting anchor rod 11 is connected with the steel grating arch by welding, or by matching in the following way, see fig. 9 and 10:

in one embodiment, the concrete grouting anchor rod further comprises two support plates 16, wherein the two support plates 16 are respectively connected to the concrete lining sections 112 of the hollow grouting anchor rods 11, and the two support plates 16 are respectively supported on two sides of the steel grating arch. Design like this, produce the support drawknot power to the steel grating bow member through the layer board, the atress area is big, and the atress is more even, and it is better to prevent the deformation effect, and the installation accuracy requires lowly moreover.

Preferably, a strip-shaped notch 161 is formed in the support plate 16, the support plate 16 is clamped on the concrete lining section 112 of the hollow grouting anchor rod 11 through the strip-shaped notch 161, the support plate 16 is matched with the concrete lining section 112 of the hollow grouting anchor rod 11 and the steel grating arch through the insertion steel bar 17 and the second nut 18, the insertion steel bar 17 comprises a middle V-shaped section 171 and two insertion sections 172 on two sides, two insertion holes 162 are formed in the rear side of the strip-shaped notch 161 on the support plate 16, the V-shaped section 171 of the insertion steel bar 17 is enclosed outside the concrete lining section 112 of the hollow grouting anchor rod 11 and is opposite to the opening of the strip-shaped notch 161, the insertion sections 172 on two sides of the insertion steel bar 17 are respectively inserted into the two insertion holes 162, the outer ring main bar 21 and the inner ring main bar 22 of the steel grating arch are limited between the V-shaped section 171 of the insertion steel bar 17, the support plate 16 and the concrete lining section 112 of the hollow grouting anchor rod 11, and the second nut 18 is screwed on the concrete lining section 112 of the hollow grouting anchor rod 11 16 form a stop. Design like this, the layer board is installed through the bar breach, and is more convenient, easy to operate, the second nut forms from the below to the layer board and supports and spacing to through the cooperation of grafting reinforcing bar and jack, can surround the concrete lining section, prevent that it from deviating from the bar breach, in addition, the outer loop owner muscle and the inner ring owner muscle of steel grating bow member are also spacing between the V-arrangement section of grafting reinforcing bar, layer board and concrete lining section, and simple structure is reasonable, and the practicality is better.

In specific implementation, after the inserted steel bars 17 are installed, the parts of the inserted steel bars, which extend out of the supporting plate 16, can be bent to prevent the inserted steel bars from falling out of the insertion holes 162.

In an embodiment, referring to fig. 11 and 12, the upper ends of the hollow grouting anchor rod 11 and the mortar anchor rod 27 are both provided with an anchor head 15, the anchor head 15 includes a V-shaped elastic sheet 151 fixed on the hollow grouting anchor rod 11 or the mortar anchor rod 27 and a spring 152 sleeved on the hollow grouting anchor rod 11 or the mortar anchor rod 27, two sides of the elastic sheet 151 are respectively provided with a strip-shaped hole 153, and the upper side hole wall of the strip-shaped hole 153 is connected with a claw 154 bent outwards. When inserting the anchor section 111 of cavity slip casting stock 11 into drilling, shell fragment 151 can self-adaptation atress adduction, spring 152 plays the effect of strutting shell fragment 151, designs like this, the anchor head plays the effect of fixed and stock placed in the middle, can produce certain anchor power moreover, improve the fastness buried underground of stock, and the anchoring agent passes the bar hole, in the jack catch stretches into the anchoring agent, can further strengthen the anchor power, improve the fastness buried underground of stock.

In one embodiment, referring to fig. 13 to 16, the steel grating arch includes an outer ring main rib 21 and an inner ring main rib 22 each having a circular arc shape, and a plurality of support reinforcing mechanisms 23 welded between the outer ring main rib 21 and the inner ring main rib 22; support reinforcing mechanism 23 includes that two fronts are the 8 font, the side is the basic reinforcing bar 231 of V-arrangement, two mutual symmetries of basic reinforcing bar 231 and middle part welding link to each other for the side that supports reinforcing mechanism 23 is the X-arrangement, a plurality of installation direction crisscross designs that support reinforcing mechanism 23, in arbitrary two adjacent reinforcing mechanism 23 that support, one of them side that supports reinforcing mechanism 23 is towards outer loop owner muscle 21, another installation direction that supports reinforcing mechanism 23 and this one of them contained angle that supports between the installation direction of reinforcing mechanism 23 are 90 degrees.

The inner ring main rib and the outer ring main rib are arc-shaped and have high degree of fit with the rock wall of the tunnel, the designed support reinforcing mechanism is simple in structure, reliable in support reinforcing effect and good in bonding effect with concrete, the mounting directions of the plurality of support reinforcing mechanisms are staggered to form supports in different postures, the support reinforcing effect is more reasonably and uniformly distributed, the effect is better, and compared with the existing steel arch frame, the flexible support structure has the advantages of a flexible support structure, can allow the tunnel surrounding rock to deform to a certain degree, has the advantages of a rigid support structure, can bear larger surrounding rock pressure, can be better applied to large-span and ultra-large-span tunnels, and is reasonable in design, light in weight, high in bearing capacity, strong in integrity, easy to manufacture and mount, simple in process, low in cost and very good in practicability.

In one embodiment, referring to fig. 13 to 16, the support reinforcement mechanism 23 further includes two ring-shaped reinforcing bars 232, and the two ring-shaped reinforcing bars 232 are respectively supported between two sides of the two foundation reinforcing bars 231 and are welded to the two foundation reinforcing bars 231. Design like this, can prevent two basic steel bars inward bending deformation through the ring reinforcing bar, further additional strengthening structural strength and stability.

In one embodiment, referring to fig. 17, the mortar anchor 27 is connected to the steel grating arch through the anchor ear 24, the first installation ring 241 and the second installation ring, the anchor ear 24 is sleeved outside the middle portion of the two foundation steel bars 231, the first installation ring 241 is welded on the anchor ear 24, the second installation ring 242 is welded on the rear end of the mortar anchor 27, and the first installation ring 241 and the second installation ring 242 are sleeved with each other. During construction, the mortar anchor rod is buried in the tunnel rock wall firstly, so that reliable anchoring force is generated between the mortar anchor rod and the tunnel rock wall, and reliable pulling force can be provided for the steel grating arch centering, so that the self-stability capability of the steel grating arch centering is improved, the deformation of the steel grating arch centering is effectively controlled, the construction difficulty is reduced, the anchor ear can be a common anchor ear sold in the market at present, on one hand, the effect of improving the structural strength of the supporting and reinforcing mechanism can be achieved, on the other hand, the position and the angle of the anchor ear can be adjusted, and the anchor ear is matched with the mobility of the first mounting ring and the second mounting ring, so that the limitation on the mounting.

In one embodiment, referring to fig. 18, each of the outer ring main ribs 21 and the inner ring main ribs 22 is composed of two reinforcing bar rods 201 and more than one first reinforcing rib 202 welded between the two reinforcing bar rods 201, and more than one second reinforcing rib 203 is welded between the outer ring main ribs 21 and the inner ring main ribs 22. The design like this, simple structure makes and installs easily, and the structure is also more reliable and stable moreover.

In one embodiment, referring to fig. 18 and 19, two tie bars 25 are respectively installed at two ends of the outer ring main bar 21 and the inner ring main bar 22, and more than one bolt hole 26 is formed on each tie bar 25. Due to the design, a plurality of novel steel grating arches in the tunnel can be conveniently spliced and installed, and the practicability is better.

The invention mainly comprises excavation, supporting and lining, preferably, blasting excavation is adopted for the excavation modes of the middle pilot tunnel, the upper step channel, the middle step left channel, the middle step right channel, the lower step left channel and the lower step right channel, so that the construction efficiency is higher and the period is shorter. The blasting construction mainly realizes the minimum disturbance of the existing line striding on a small angle by a digital electronic detonator, a three-step method and a middle pilot tunnel in advance, and the support and lining mainly complete the support protection of surrounding rocks by primary support and secondary lining construction.

The blasting excavation process flow is as follows: hole arrangement → drilling → charging → plugging → networking → protection → warning → priming → post explosion inspection → disarm, as follows:

1) cloth hole

The hole distribution is carried out by technicians according to the hole network parameters of the design scheme, when the hole distribution meets geological conditions such as cracks or faults, the hole distribution needs to be properly adjusted, and the specific arrangement and initiation sequence of the blastholes are respectively shown in figure 8. When the blast hole opening is adjusted, the blast hole direction is slightly adjusted as much as possible, so that the blasting square amount born by blasting of each blast hole is approximately balanced, wherein the schematic cross-sectional view of the undercut hole is shown in fig. 8. The blasting parameters are shown in table 1. The specific principle of blast hole arrangement is as follows:

firstly, blast holes are prevented from being arranged in places with loose rocks, joint crack development or large lithological change as far as possible;

secondly, paying special attention to the place with the too large chassis resistance line, adopting a blast hole encryption mode to avoid generating a root bottom according to different conditions;

thirdly, the change of the resistance line of the blast holes in the front row is specially noticed, so that the accidents of blasting flying stones caused by the over-small resistance line and the remaining of a sill caused by the over-large resistance line are prevented;

and fourthly, paying attention to the change of the elevation of the terrain, properly adjusting the drilling depth and ensuring that the elevation of the lower operation platform is basically consistent.

TABLE 1 blasting parameter table

2) Drilling holes

Drilling according to the hole distribution position, the drilling direction and the drilling depth required by the design scheme; before drilling, whether the drilling machine is normal or not must be carefully checked, and broken slag and the like are prevented from falling into the hole to block the blast hole.

3) Hole inspection

The technical personnel use a gun rod or a tape measure to check the row pitch, the hole direction and the hole depth of the holes one by one, and if the requirements are not met, the hole is corrected in time; rechecking the resistance lines of the blast holes in the front row and checking the water content in the holes; and after the detection, hole checking recording is carried out and is used as a calculation basis for blasting charge.

4) Medicine charge

Carrying out blast hole charging of each blasting operation according to single-hole charging amount allowed by a blasting scheme approved by a public security organization, wherein a main blast hole for deep hole blasting and a blast hole for shallow hole blasting adopt a coupled charging structure, and a gun rod is used for measuring the hole depth at any time in the charging process to prevent insufficient filling length caused by hole blocking during charging; the remaining holes are filled to the muzzle with rock debris or stemming.

5) Packing

The packing material is typically drilled and filled with drill cuttings, clay, and coarse sand and is deposited around the blast hole. When the horizontal hole is filled, the drilling cuttings, clay, coarse sand and the like are made into a stemming roll according to the diameter requirement of the blast hole by using newspaper and the like, and the stemming roll is placed around the blast hole.

The explosive charging structure shown in figure 7 can be adopted, and comprises explosive 31, stemming 32, bamboo chips 33, a detonating cord 34 and a non-electric millisecond detonator 35, wherein the explosive charging structure is connected through the detonating cord, the explosive charging structure is bound through the bamboo chips, and the detonating tube detonator is detonated.

6) Networking

The technical personnel or experienced skilled blasting personnel carry out connection according to the network connection mode determined by the blasting scheme, strictly control the single-section blasting explosive quantity of the blasting, and a specially-assigned person is responsible for rechecking and recording the single-hole explosive quantity and the single-section blasting explosive quantity of each blast hole, rechecking the delay section position of each hole detonator and the network connection quality, and blasting can be carried out after safety supervision and rechecking confirmation.

7) Protection

Because the nearest distance between the blasting area and the natural gas pipeline is within the range of 200m, the orifice protection adopts a braided belt to fill the screened fine river sand protection, and then adopts a flexible rubber pad to perform surface layer protection.

8) Warning

According to the requirements of blasting safety regulations, the safety distance between personnel and equipment is set to be 200m during deep hole blasting, and the safety distance between the personnel and the equipment is set to be 300m during shallow hole blasting. The alarm range of the storage point and the charging operation area of the blasting equipment is 50m, and smoking and fire are strictly forbidden in the range

9) Initiation of detonation

Detonation is the key to blasting. Because the existing initiation instruments produced in China are susceptible to the influence of human operation factors, the failure of the whole blasting can be caused by a small error of an initiation person (for example, battery replacement is forgotten, discharging is not carried out according to requirements before wiring, operation sequence is wrong, a button is not pressed to the bottom, switch contact is poor, the initiation button is pressed to be not in place in advance, and the like), so that the requirement on the initiation person is high.

In order to realize the minimum disturbance to the existing line, the construction method adopts advanced digital electronic detonator control, and is a novel electric detonator which can be adjusted at will and realize accurate delay firing time, a Longxin No. 1 electronic detonator is arranged in the novel electric detonator, has two-wire bidirectional non-polar networking communication, in-hole on-line programming and full-function detection capability, can carry out on-line detection on the integrity of a blasting network, can realize in-hole setting and on-line calibration of delay time in a wide range (0-16000 ms) and a small interval (1ms), can effectively manage the initiation energy, and has the characteristics of good initiation accuracy, high initiation reliability, good use safety, water resistance, pressure resistance, impact resistance, environmental protection and the like. The detonator is internally provided with a product serial number and a detonation password, an anti-interference isolation circuit is embedded, the use is safe, the network design is simple, the operation and the use are convenient, and the main technical indexes of the Longxin No. 1 digital electronic detonator are shown in a table 2.

Compared with a non-electric detonator network, the digital electronic detonator has the advantages that the inspectability of the detonator and the blasting network is mainly reflected. After the detonating network is connected, all constructors are evacuated beyond a safe distance, one-key detection can be carried out on the reliability of the detonating network connection through special equipment, and the detonator which is unreliable in connection is accurately positioned, so that the detonating network is safe and efficient. Firstly, the interference vibration reduction in the real sense can be realized through the differential blasting; secondly, the good synchronism ensures the light explosion and pre-splitting effect; thirdly, the single initiation explosive quantity can be increased by a hole-by-hole initiation method, and the single initiation scale is improved; fourthly, by setting the differential time on line, the stress generated by rock explosion is fully utilized, and the crushing effect is improved. These are incomparable with conventional detonators.

Table 2 longxin No. 1 digital electronic detonator main technical index

Serial number	Name (R)	Index (I)
			1	Delay accuracy	0-100 ms, and deviation is less than 1 ms; 101-16000 ms, and the deviation is less than 1%.
2	Extent of delay	The minimum time interval is 1ms within the range of 0-16000 ms.
			3	Programming mode	And programming on line.
4	Detection mode	And (5) online monitoring.
			5	Initiation mode	Double-code initiation: and the detonator login password and the detonation authorization password.
6	Communication system	Two-wire two-way non-polar networking communication.
			7	Property of carrying electricity outside	220VAC, 50VDC, 15KV electrostatic, radio frequency and stray current.
8	Water resistance	30m
			9	High temperature oil resistance	35# diesel oil, 80 ℃, 72 h.
10	Temperature of use	-20℃～+70℃。

10) Post-detonation examination

And (4) entering an explosion area by an exploding operator or a safety operator, checking whether potential safety hazards exist or not, and making treatment measures in time.

The post-detonation examination content comprises:

the method includes the steps of firstly, whether blind cannons exist or not. Whether blind cannons exist is preliminarily judged through the accumulation condition.

② accumulation condition. Whether rock accumulation condition of rock-soil blasting is stable, whether buildings (structures) completely collapse during demolition blasting, and whether potential safety hazards exist.

And thirdly, the side slope (or surrounding rock) is in danger of rocks. Whether the side slope after the open blasting is stable or not, whether dangerous stones exist on the side slope or not, whether roof fall exists in the underground blasting or not, whether a roof is still suspended by the dangerous stones or not, whether the support is damaged or not and the like.

And nearby buildings and equipment (including natural gas pipelines) which cannot be evacuated have no damage.

Whether there is any remaining blasting equipment on site.

Due to the possible existence of factors such as delayed explosion and harming human bodies by the blast smoke, a certain waiting time after explosion is required. The inspection personnel entering the blast area of the project obey the following waiting time regulations:

and (3) performing open-air shallow hole blasting, wherein the time after blasting is more than 5 minutes, performing large-scale open-air deep hole blasting, and the time after blasting is more than 15 minutes, so that inspectors can be admitted to the blasting site.

11) Disarm

After detonation, the inspection confirms that no blind shot or other dangerous cases exist, and the inspection personnel can remove the blasting safety warning after reporting to the blasting work leader.

The specific flow and the cautions of the preliminary bracing are as follows:

1) sprayed concrete

And a wet spraying manipulator is adopted for construction on site, and the spraying materials are uniformly mixed and delivered by a mixing station. And cleaning a sprayed surface before spraying the concrete, checking the excavation size, cleaning scum and deposits, and embedding and controlling the thickness mark of the concrete. The spraying operation should be carried out in layers, segments and segments, the spraying sequence is from bottom to top, and the segment length is not more than 6 m. Blasting operation is carried out 3 hours after the sprayed concrete is finally set. And curing the sprayed concrete after final setting for 2h, wherein the surface of the sprayed concrete is required to be dense and smooth without cracks, leaking spray, leaking ribs and the like.

2) Anchor rod construction

The anchor rod for the large-span primary support design is as follows: side wall

Mortar anchor and arch

And (4) combining the hollow grouting anchor rod.

Positioning is firstly carried out before drilling of the anchor rod, and the hole opening position of the anchor rod is determined. The surrounding rock is checked before drilling, whether the phenomena of block falling and cracking exist or not is checked, and the construction safety is ensured. And (4) cleaning the hole by adopting high-pressure air after the anchor rod is formed into the hole, and checking whether the depth of the anchor rod hole meets the requirement. The anchor rod construction should install the backing plate, and after the sand body intensity reaches 10MPa, the backing plate is fastened with the nut and is hugged closely with the spray layer face. The anchor rod cannot be knocked randomly after being installed, and a heavy object cannot be hung on the end part of the anchor rod before the filling mortar is finally set.

3) Construction of reinforcing mesh

The reinforcing bar net is uniformly and intensively manufactured in a processing plant according to design requirements, and the size of the reinforcing bar net is convenient to transport and install. The reinforcing mesh is paved after the concrete is sprayed for the first time, so that the reinforcing mesh and the sprayed concrete form a whole. The lapping length of the reinforcing mesh is 1-2 meshes, and the reinforcing mesh is firmly connected with the anchor rod. The protective layer of the reinforcing mesh is not less than 2 cm.

4) The steel arch of the grid is a supporting framework structure made of profile steel (grid) which is distributed according to the tunnel excavation contour line for keeping the stability of surrounding rocks during the primary supporting period of tunnel excavation, the purpose of supporting the stability of the surrounding rocks and limiting the deformation of the surrounding rocks can be achieved after the steel frame is installed, the steel arch is usually combined with a steel bar net, sprayed concrete and the like to bear force together, and the expansion and longitudinal connection steel bars of the steel arch of the grid are shown in a figure 20.

The primary support steel frames are processed and distributed in a unified mode by a steel bar processing factory, and the steel frames leave the factory and are assembled in a trial mode. The steel frame is erected after the initial spraying, and the virtual slag and sundries are removed before the installation. When the steel frame is installed, all the steel frame connecting plates are firmly and closely connected through bolts, and the outer edge of the steel frame is tightly wedged with the primary sprayed concrete by using concrete precast blocks every 2 m. The steel frame is firmly welded with the foot locking anchor rod. The gap behind the steel frame is filled with sprayed concrete, the concrete between the steel frame and the wall surface is sprayed during construction, and the concrete between the steel frames is sprayed afterwards.

Each unit of grid steel is formed by welding main ribs, reinforcing ribs and connecting angle steel, the steel frame is suitable for being prefabricated on site, the units are connected through bolts, side walls, foot pads and steel plates, and welding seams at joints are strictly performed according to the relevant requirements of the steel structure.

The steel arch frame of the grid is erected after the concrete with the length of 4cm is initially sprayed, the concrete is sprayed again after the erection is finished, and the coverage thickness of not less than 3cm is guaranteed. The adjacent steel frames are connected by adopting middle 22 steel bars, the circumferential distance is 1.0m, and the steel bars are obliquely arranged.

The large span section span is large, the primary support steel frame adopts 150 grids, 160 grids and I18I-steel, the steel frame self-stability is poor, the potential safety hazard exists during construction, reinforcement measures must be taken during steel frame construction, a group of mortar anchor rods are respectively added at the arch crown and the arch waists at two sides of the primary support steel frame on site, and the mortar anchor rods adopt

The deformed steel bar, stock anchor length are not less than 1m, and the stock is personally submitted 45 contained angles with the excavation and is beaten and establish, and the same steelframe interval of stock longitudinal separation distance. Anchor rod tip flushes the anchor rod with the steelframe outside and adopts the welding with the steelframe, increases primary support steelframe stability, as shown in fig. 6.

The specific process and considerations for inverted arch and lining construction are as follows:

1) inverted arch excavation

The temporary passing of construction establishes the invert trestle and stridees across, and invert excavation length control is within 3m, and in order to avoid both sides preliminary bracing unsettled, can increase some temporary supports in hunch foot department, ensure structure safety.

According to the distribution condition of tunnel surrounding rocks, drilling and blasting excavation is mainly adopted for inverted arch excavation, and manual cooperation with mechanical excavation is adopted as assistance; the foundation excavation should be smooth and flat, the underexcavation should not be carried out, and the over-excavation part is backfilled by applying the same-grade concrete.

The inverted arch is subjected to deslagging by using a dump truck, and scum on the inverted arch is removed in time after deslagging.

2) Inverted arch concrete pouring

And (3) performing inverted arch concrete construction in time after 2 cycles of primary support at the bottom of the tunnel, wherein the inverted arch of the same section must be continuously cast without division casting. And (4) checking the size and elevation of the tunnel bottom after the tunnel bottom is cleared, if the tunnel bottom is excavated, cleaning floating slag, sundries and accumulated water, and after the cleaning is finished, performing quality inspection and acceptance by a quality inspection engineer and a supervision engineer after the team self-inspection is qualified, and then erecting a mold and pouring concrete.

(3) Lining construction

The tunnel lining construction follows the principle of 'inverted arch advancing and arch wall integral lining', after primary support is completed, in order to effectively control the deformation of the inverted arch, the inverted arch is constructed following the tunnel face, and the inverted arch filling adopts a simple trestle platform to solve the problem of transportation in the tunnel.

And (3) tunnel waterproof construction: and waterproof materials are paved in the tunnel by adopting a waterproof board rack.

And (3) tunnel steel bar construction: and (4) processing in a centralized steel bar processing factory, transporting to a second lining steel bar construction part in the tunnel, and performing steel bar construction by adopting a second lining steel bar installation trolley.

And (3) construction of tunnel secondary lining concrete: the concrete is uniformly delivered by a mixing station, and is pumped into a die by a ground pump, and the vibration is carried out by adopting an attached vibrator and a tamping bar in a manual matching manner.

The construction method is applied to a GSSG-10 Bingzhen tunnel engineering test and formal application of the newly-built Jiangzhou to Shenzhen railway, proves that the construction method is safe, rapid and reliable, and obtains good economic and social benefits. The key technology of the construction method reaches the domestic advanced level. A new idea is created for the existing blast construction method of the high-speed rail large-span tunnel, the forming method is specially summarized for further popularization and application, and the method is suitable for blast excavation of various newly-built tunnels across the existing line at small angles.

It should be understood that the examples and embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure, and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this disclosure.

Claims

1. The construction method for spanning the existing line at a small angle of a newly-built tunnel is characterized in that: the method comprises the following steps:

2. The construction method for existing lines spanning over small angles of a newly built tunnel according to claim 1, characterized in that: further comprising the step (11): and (3) pouring inverted arches at the bottoms of the front ends of the left channel and the right channel of the lower step, filling the inverted arches, and finally pouring secondary lining.

3. The construction method for constructing the newly-built tunnel to span the existing line at a small angle according to claim 1 or 2, wherein: blasting excavation modes are adopted for the middle pilot tunnel, the upper step channel, the middle step left channel, the middle step right channel, the lower step left channel and the lower step right channel.

4. The construction method for constructing the newly-built tunnel to span the existing line at a small angle according to claim 1 or 2, wherein: the concrete construction method of the primary support comprises the following steps: the concrete is sprayed firstly, then the anchor rod group is installed, then the reinforcing mesh is laid, finally the steel grating arch is installed, and the anchor rod group is connected with the steel grating arch.

5. The construction method for existing lines spanning over small angles of a newly built tunnel according to claim 4, characterized in that: the anchor rod group comprises a plurality of hollow grouting anchor rods and a plurality of mortar anchor rods, the hollow grouting anchor rods are arranged along the circumferential direction and the longitudinal direction of the steel grating arch according to a quincunx shape, and the mortar anchor rods are arranged at the arch crown and the arch waists at two sides.

6. The construction method for existing lines spanning over small angles of a newly built tunnel according to claim 5, wherein: the hollow grouting anchor rod is provided with external threads, the hollow grouting anchor rod is sequentially divided into an anchoring section, a concrete lining section and a template reinforcing section from top to bottom, the anchoring section of the hollow grouting anchor rod is embedded in a tunnel rock wall through an anchoring agent, the hollow grouting anchor rod is sleeved with a sealing ring, a water stop steel ring and a first nut, the sealing ring and the water stop steel ring are clamped between the tunnel rock wall and the first nut, the sealing ring is tightly attached to the tunnel rock wall, and the concrete lining section of the hollow grouting anchor rod is connected with the steel grating arch frame.

7. The construction method for existing lines spanning over small angles of a newly built tunnel according to claim 4, characterized in that: the anchor head is all installed to the upper end of cavity slip casting stock and mortar stock, and the anchor head is established the spring on cavity slip casting stock or mortar stock including fixing the shell fragment that is the V-arrangement on cavity slip casting stock or mortar stock and cover, and the both sides of shell fragment are opened the bar hole respectively, are connected with the jack catch of outwards bending on the upside pore wall in bar hole.

8. The construction method for existing lines spanning over small angles of a newly built tunnel according to claim 4, characterized in that: the steel grating arch comprises an outer ring main rib and an inner ring main rib which are both arc-shaped, and a plurality of supporting and reinforcing mechanisms welded between the outer ring main rib and the inner ring main rib; support reinforcing mechanism and include that two fronts are the 8 fonts, the side is the basic reinforcing bar of V-arrangement, two mutual symmetries of basic reinforcing bar and middle part welding link to each other for the side that supports reinforcing mechanism is the X-arrangement, a plurality of installation direction staggered designs that support reinforcing mechanism, in arbitrary two adjacent support reinforcing mechanism, one of them side that supports reinforcing mechanism is towards outer loop owner muscle, another installation direction that supports reinforcing mechanism and this one of them contained angle that supports between the installation direction of reinforcing mechanism are 90 degrees.

9. The construction method for existing lines spanning over small angles of a newly built tunnel according to claim 8, characterized in that: the supporting and reinforcing mechanism further comprises two circular ring reinforcing steel bars, and the two circular ring reinforcing steel bars are respectively supported between two sides of the two foundation reinforcing steel bars and are connected with the two foundation reinforcing steel bars in a welding mode.